Bleed is something that is required on your artwork file if you require your printing to go right to the edge. On your file, you will need to generally allow a 3mm overlap of colour larger than your final printed size that is cut off after printing to have the print run all the way to the edges.
There will be different requirements for your file depending on what it is you are getting printed and also your quantity, your artwork will require a different setup depending on if I am doing in-house printing or using the commercial printer.
Before you spend too much time with your designer finalising your file, it is best you discuss your print quantities and set up to save time.
If you need help setting up your artwork file with bleed, please just ask 🙂